1. Field of the Invention
The present invention relates generally to a sheet plate for a DC motor and, more particularly, to a sheet plate for a DC motor, in which a brush holder manufactured as a separate member is coupled to the sheet plate of the DC motor, thus effectively guiding movement of a brush and a pigtail, in addition to affording good space utilization.
2. Description of the Related Art
Generally, a vehicle is constructed to control a driving direction thereof by manipulating a steering wheel connected to wheels. However, when resistance between the wheels and a road surface is large or obstacles to steering occur, a manipulation force is weakened, so that rapid manipulation may be difficult. In order to solve the problem, a power steering device is used. The power steering device involves a power unit to manipulate the steering wheel, thus reducing a manipulating force.
The power steering device includes an electronic control unit (ECU), a torque angle sensor (TAS), a torque index sensor (TIS), and an EPS motor.
The ECU drives the EPS motor in response to data on rotation of the steering wheel detected by the TAS or TIS. The EPS motor assists the rotation of a steering shaft which rotates in conjunction with the rotation of the steering wheel to change a driving direction of wheels, thus allowing a driver to rotate the steering wheel with a small force.
Such a power steering device includes a steering system extending from the steering wheel to both wheels, and an auxiliary power unit supplying auxiliary steering power to the steering system.
The auxiliary power unit includes a motor generating auxiliary power based on a control signal transmitted from the ECU, and a gear train transmitting auxiliary power from the motor to the steering shaft. The motor generally includes a motor shaft, a sheet plate, a commutator, a brush, a magnet, etc.
FIG. 1 is a plan view showing a conventional sheet plate.
The sheet plate 10 is a molding product shaped like a disc. A through hole 11 is formed through a central portion of the sheet plate 10 to allow a motor shaft (not shown) to pass therethrough, and brushes (not shown) are provided on a lower surface of the sheet plate 10.
Each brush is coupled to the sheet plate 10 by inserting the brush into a brush holder 20 that is coupled to the lower surface of the sheet plate 10. One end of the brush is exposed toward the through hole 11 and is connected to the commutator (not shown).
Meanwhile, a pigtail 31 is connected to each brush to cause current to flow to the commutator, and extends outwards along a predetermined guide portion formed on the brush holder 20.
Since the brush is in frictional contact with the commutator, the brush moves in the brush holder 20 in a diametric direction of the sheet plate 10. As each brush moves, the pigtail 31 moves in the diametric direction together with the brush.
Generally, the brush holder 20 is integrated with the sheet plate 10 and is made of a plastic material. As the brush 30 and the pigtail 31 move, the brush holder 20 is frequently deformed or damaged by frictional heat.
Further, the conventional sheet plate is problematic in that a space of the guide portion for guiding the movement of the pigtail 31 is small, and the guide portion is adjacent to the lower surface of the sheet plate 10, so that the pigtail 31 may be damaged.
Furthermore, it is difficult to install the brush 30 or the pigtail 31 due to a spatial problem, thus causing an inefficient production process.
Further, pigtails 31 pulled out from neighboring brush holders 20 are moved along a predetermined hole formed through the sheet plate 10 to an upper surface while being adjacent to each other. Since each pigtail 31 may move by a predetermined range by the movement of the brush, the neighboring pigtails 31 may be brought into contact with each other, thus causing an electric short circuit and malfunction.